The invention relates to a motor vehicle, in particular a passenger car. The invention also relates to a process for braking a vehicle in the event of a crash.
DE 36 37 165 A1 discloses a motor vehicle fitted with a crash detection device that detects an imminent collision between the vehicle and an obstacle. Depending on the collision risk it is possible to trigger various alarm levels and implement suitable counter measures adapted to the degree of danger determined in the situation.
DE 10 2005 009 949 A1 discloses a vehicle fitted with an additional braking device on its underside that can be activated when a crash detection device detects that a collision between the vehicle and an obstacle is unavoidable. The additional braking device can provide an additional friction surface that pushes away from a surface suitable for traffic. Similarly, the additional braking device can be designed as a spike so that when activated it at least partially penetrates the road surface in the manner of an anchor. Furthermore, a belt tensioning device is used to generate a haptic warning signal before brake intervention.
DE 10 2005 062 279 A1 discloses a vehicle with an additional braking device that has an essentially closed brake cushion arranged on the floor of the vehicle. The brake cushion can be expanded from an idle state and achieves a braking effect when in its expanded, active state. A crash detection device can be provided to activate the brake cushion.
DE 10 2004 052 352 B3 discloses a brake circuit for a motor vehicle comprising a brake line to receive a pressurized fluid and a reservoir connected to the brake circuit with a pressurized fluid chamber to receive additional pressurized fluid. To increase vehicle passenger safety it is possible to provide in the reservoir means by which the pressurized fluid located in the reservoir can be conveyed into the brake line and removed from it again suddenly. In conjunction with a crash detection device it is therefore possible to significantly increase the deceleration effect of the wheel brake system immediately before the vehicle collides with an obstacle.
Exemplary embodiments of the present invention address the problem of specifying an improved design for a vehicle of the type discussed above and for a braking process which is characterised by the fact that it permits greater passenger protection in the event of a collision between the vehicle and an obstacle.
Exemplary embodiments of the present invention involve a motor vehicle includes a crash detection device that detects an imminent collision between the vehicle and an obstacle and a vehicle lifting device that cooperates with the crash detection device in order to compensate suddenly for a brake diving movement of the vehicle before the vehicle collides with the obstacle.
Exemplary embodiments of the present invention also provide a method involving detecting, by a crash detection device, an imminent collision between a vehicle and an obstacle and compensating, by a vehicle lifting device that cooperates with the crash detection device, for a brake diving movement of the vehicle before the vehicle collides with the obstacle.
Exemplary embodiments of the present invention compensate for a pitching movement of the vehicle that is caused by a torque acting on the vehicle during braking immediately before the vehicle collides with the obstacle. The pitching movement generated when the vehicle brakes causes the front end of the vehicle to dip and the rear end of the vehicle to lift. The dipping of the front end of the vehicle during braking is also referred to as a brake diving movement or brake diving. Exemplary embodiments of the present invention compensate for the front-end pitching movement, which is the brake diving, immediately before the crash, i.e. to lift the front of the vehicle back essentially to its original height shortly before the collision. Accordingly, the present invention recognizes that there is an increased risk of injury for the vehicle passengers if the vehicle runs underneath an obstacle in the event of a crash. The risk of running under the obstacle is increased by brake diving. Accordingly, the compensation for brake diving immediately before the crash reduces the risk of running under the obstacle. To compensate for brake diving in the event of a crash immediately before the vehicle collides with the obstacle, exemplary embodiments of the present invention fit the vehicle with a specially adapted vehicle lifting device. This is able to lift the front of the vehicle quickly, promptly or suddenly to compensate for the lowering of the front end of the vehicle caused by the brake diving movement quickly and/or for a short period.
The sudden compensation achieves relatively high vertical accelerations. For example, the vertical acceleration achieved in the front region of the vehicle can reach the level of gravitational acceleration. This can temporarily almost double the force with which front region of the vehicle is pushed away from the road surface. Accordingly, the effective braking forces can also be doubled for a short period. The sudden compensating movement therefore has the additional effect of being able to significantly increase the braking effect immediately before the collision. This permits any force spikes occurring in the event of a crash to be reduced, thereby lowing the risk of injury to the vehicle passengers.
In accordance with one aspect of the present invention, it is possible to provide a safety belt system fitted with a belt tensioning device, the crash detection device co-operating with the belt tensioning device and being designed and/or programmed such that in the event of a crash it causes the belt tensioning device to reduce belt slackness in the safety belt system depending on the point in time at which the vehicle lifting device is activated. This development makes use of the knowledge that the sudden lifting of the vehicle leads to the vehicle passenger being pressed into the seat. In this process a safety belt may loosen, thereby creating or increasing belt slackness, i.e., a section of belt with reduced tension or an untensioned, loose section of belt. The targeted coordination of the belt tensioning device with the vehicle lifting device permits the passenger to be held particularly tightly in the vehicle seat, thus reducing relative movements and consequently force spikes in the event of a crash. The reduction of belt slackness using the belt tensioning device is usefully effected suddenly.
In this context the term “belt slackness” refers to a section of a safety belt which is loose or is pre-tensioned less than the desired level of pre-tensioning. The belt tensioning device reduces this belt slackness by increasing the pre-tensioning in the belt. For example, this may be achieved by rolling or retracting the belt into a belt roller with increased restoring force. A belt tensioning device of this type can operate using an electric motor or pyrotechnically.
In accordance with an aspect of the present invention, the crash detection device can be designed and/or programmed such that it causes the belt tensioning device to activate the vehicle lifting device with a time delay in order to reduce the belt slackness. Thus, it is possible to tighten the belt at exactly the moment the greatest belt slackness occurs in the safety belt system due to the lifting of the vehicle. This optimizes the manner in which the passenger is held in the vehicle seat.
In accordance with a further aspect of the present invention, the belt tensioning device can be designed such that in the event of a crash it permits belt slackness to be reduced in two or more stages. The crash detection device can usefully be designed and/or programmed such that in the event of a crash it causes the belt tensioning device to make a first reduction of the belt slackness before the activation of the vehicle lifting device and to make a second reduction of the belt slackness after the activation of the vehicle lifting device. This two- or multi-stage reduction of the belt slackness, timed in coordination with the activation of the vehicle lifting device, optimizes the “strapping” of the vehicle passenger into the vehicle seat. During the first reduction, which takes place before the activation of the vehicle lifting device, the usual belt slackness during normal driving is removed or the safety belt tightened. This achieves a certain amount of pre-tensioning. The second reduction, which takes place after the activation of the vehicle lifting device, is able to remove from the safety belt system the belt slackness created by the sudden lifting of the vehicle and thus the sudden pushing of the passenger into the seat. These two reductions may differ from one another in terms of tractive force and/or duration and/or speed.
In accordance with a further aspect of the present invention, a seat lifting device can be provided to lift a vehicle seat or at least a seat cushion of the vehicle seat in relation to the rest of the vehicle. The crash detection device is able to cooperate with this seat lifting device and, furthermore, can be designed and/or programmed such that in the event of a crash it causes the seat lifting device to lift the vehicle seat and/or at least the seat cushion dependent on the point in time at which the vehicle lifting device is activated. The lifting of the vehicle seat and/or seat cushion can increase belt pre-tensioning that can simultaneously also lead to a reduction of belt slackness. Holding the passenger more tightly in the vehicle seat leads to a reduction in the risk of injury.
It is clear that tensioning the safety belt by lifting the vehicle seat and/or the seat cushion is possible only when at least one of the fixing points of the safety belt is made quickly to the vehicle and does not lift with the vehicle seat and/or the seat cushion. In the case of a 3-point safety belt, for example, the two lower fixing points next to the seat cushion can be fixed to a seat anchorage on the vehicle.
An exemplary aspect of the present invention also provides for a crash detection device designed and/or programmed such that in the event of a crash it causes the seat lifting device to activate the belt tensioning device with a time delay. This ensures that the tensioning of the safety belt that can be achieved using the seat lifting device comes in addition to the tensioning achieved with the belt tensioning device and that as a result the passenger can be held more tightly in the vehicle seat.
In accordance with another aspect of the present invention, the vehicle lifting device can be designed such that it carries out the sudden compensation for the brake diving movement immediately before the vehicle collides with the obstacle. This means that the greatest brake deceleration can be used particularly effectively immediately before the collision and a temporary lifting of the vehicle is sufficient, thereby simplifying the structure of the vehicle lifting device.
The vehicle lifting device can have a pushing body that pushes away from a road surface to compensate for the brake diving movement in a front region of the vehicle. In this manner it is comparatively simple to achieve effective lifting of the front region of the vehicle.
In accordance with an aspect of the present invention, at least the underside of the pushing body facing the road surface is designed as a braking body such that an additional braking force can be transmitted to the vehicle when the pushing body makes contact with the road surface. Due to this design of pushing body, the lifting of the front of the vehicle to compensate for the brake diving movement can be used to generate an additional braking force, thereby increasing the deceleration of the vehicle immediately before the collision and reducing the risk of injury to vehicle passengers.
Further important features and advantages of the invention are detailed in the subsidiary claims, in the drawings and in the related descriptions of the figures with reference to the drawings.
It is understood that the features specified above and those to be explained below can be used not only in the combination disclosed here but also in other combinations or alone without leaving the framework of the invention.
Preferred embodiments of the invention are shown in the drawings and described in greater detail below, identical reference numerals being used to refer to components which are identical or similar or functionally identical.